Slick 60's

My truck developed a tapping sound comming from the drivers side valve cover. It only does it when it is warm, and it gets faster a i rev the engine. Is it a valve knock or something else and how so i correct it??

Matt, what size or type of engine?

I am assuming its the 352 in your F100? and if so I would almost have to assume again, that it could possibly be a bent pushrod. you might want to just pop that valve cover off and have a looksie.

Yeah its a 352. I'll go out and pop the valve cover and take a look.

If you start it for a very short time with the cover removed it will be messy but you might actually see whats going wrong too. If a rocker is the culprit its probably actually the push rod. Rockers don't just come out of adjustment. It happens more slowly due to wear. If it happens all of a sudden there is another problem. Generally the push rod bent/failed. They too can fatigue and fail after a certain age and enough Hot / Cold cycles.

I dont think he will actually need to start it, thats a last resort lol. just look all the valvetrain over closely, and can turn it over by hand with the crankshaft bolt and a socket. or have someone bump the starter a few times to see if everything is moving smoothly. I always made good practice to put each cylinder at TDC for these diagnostics and check play in the rockers as I go from cylinder to cylinder. Usually if a valve gets caught up inside its chamber somehow, either due to carbon buildup, or loss of lubrication and seizure then the pushrod can get bent. I would guess the 352 is a shaft rocker system with non adjustable rockers ( hydraulic) so check the bolts on the shaft also